Chapter U4.77, Problem 5E

(a)

Interpretation Introduction

Interpretation:

Between 10.0 g of calcium ( $\text{Ca}$ ) and 10.0 g of calcium chloride ( ${\text{CaCl}}_2$ ), the molecule having more number of moles of metal atoms should be determined.

Concept Introduction:

Mole is SI unit which is used to measure the quantity of the substance. It is the quantity of a substance which contains same number of atoms as present in accurately 12.00 g of carbon-12 is known as mole

Number of moles is defined as the ratio of mass to the molar mass.

  $\text{Number of moles = }\frac{\text{Mass (g)}}{\text{Molar mass}}$

The ratio of mass of the given compound to the number of moles of compound is known as molar mass.

The one mole of any substance is equal to the Avogadro number i.e. $6.022\times {10}^{23}$ atoms.

Answer to Problem 5E

Number of moles of calcium atom is more in 10 g of calcium in comparison to 10 g of calcium chloride.

Explanation of Solution

The given information is: 10.0 g of calcium ( $\text{Ca}$ ) and 10.0 g of calcium chloride ( ${\text{CaCl}}_2$ )

First step is to calculate the molar mass of each molecule.

Molar mass of calcium = $40.078\text{ g/mole}$

Molar mass of calcium chloride = $\text{1}\times \text{40}\text{.078 g/mole + 2}\times \text{35}\text{.45 g/mole}$

= $110.98\text{ g/mole}$

Now,

Number of moles of calcium metal is calculated as:

  $\text{Number of moles = }\frac{\text{Mass (g)}}{\text{Molar mass}}$

Put the values,

Number of moles of calcium metal = $\frac{\text{10}\text{.0 g}}{\text{40}\text{.078 g/mole}}$

Number of moles of calcium metal = $\text{0}\text{.25 mole}$

Number of moles of calcium chloride is calculated as:

  $\text{Number of moles = }\frac{\text{Mass (g)}}{\text{Molar mass}}$

Number of moles of calcium chloride = $\frac{\text{10}\text{.0 g}}{110.98\text{ g/mole}}$

Number of moles of calcium chloride = $\text{0}\text{.090 mole}$

In one mole of calcium chloride, ${\text{CaCl}}_{\text{2}}$ there is one mole of calcium ion and two moles chloride ions as shown:

  ${\text{CaCl}}_{\text{2}}\to {\text{ Ca}}^{\text{2+}}{\text{ + 2Cl}}^{-}$

So, the number of moles of calcium metal ion in $\text{0}\text{.090 mole}$ of calcium chloride is $\text{0}\text{.090 mole}$ .

Hence, number of moles of calcium atom is more in calcium in comparison to calcium chloride.

(b)

Interpretation Introduction

Interpretation:

Between 5.0 g of sodium chloride ( $\text{NaCl}$ ) and 5.0 g of sodium fluoride ( $\text{NaF}$ ), the molecule having more number of moles of metal atoms should be determined.

Concept Introduction:

Mole is SI unit which is used to measure the quantity of the substance. It is the quantity of a substance which contains same number of atoms as present in accurately 12.00 g of carbon-12 is known as mole

Number of moles is defined as the ratio of mass to the molar mass.

  $\text{Number of moles = }\frac{\text{Mass (g)}}{\text{Molar mass}}$

The ratio of mass of the given compound to the number of moles of compound is known as molar mass.

The one mole of any substance is equal to the Avogadro number i.e. $6.022\times {10}^{23}$ atoms.

Answer to Problem 5E

Number of moles of sodium atom is more in 5.0 g of sodium fluoride in comparison to 5.0 g of sodium chloride.

Explanation of Solution

The given information is: 5.0 g of sodium chloride ( $\text{NaCl}$ ) and 5.0 g of sodium fluoride ( $\text{NaF}$ )

First step is to calculate the molar mass of each molecule.

Molar mass of sodium chloride = $1\times 23.0\text{ g/mole + 1}\times \text{35}\text{.45 g/mole}$

= $58.45\text{ g/mole}$

Molar mass of sodium fluoride = $\text{1}\times \text{23}\text{.0 g/mole + 1}\times \text{19}\text{.0 g/mole}$

= $42.0\text{ g/mole}$

Now,

Number of moles of sodium chloride is calculated as:

  $\text{Number of moles = }\frac{\text{Mass (g)}}{\text{Molar mass}}$

Put the values,

Number of moles of sodium chloride = $\frac{\text{5}\text{.0 g}}{\text{58}\text{.45 g/mole}}$

Number of moles of sodium chloride = $\text{0}\text{.0855 mole}$

Number of moles of sodium fluoride is calculated as:

  $\text{Number of moles = }\frac{\text{Mass (g)}}{\text{Molar mass}}$

Number of moles of sodium fluoride = $\frac{\text{5}\text{.0 g}}{42.0\text{ g/mole}}$

Number of moles of sodium fluoride = $\text{0}\text{.119 mole}$

The number of metal atoms, ${\text{Na}}^{\text{+}}$ in both the compounds is 1 as shown:

  $\text{NaCl}\to {\text{Na}}^{\text{+}}{\text{ + Cl}}^{-}$

  $\text{NaF}\to {\text{Na}}^{\text{+}}{\text{ + F}}^{-}$

Hence, number of moles of sodium atom is more in sodium fluoride in comparison to sodium chloride.

(c)

Interpretation Introduction

Interpretation:

Between 2.0 g of iron oxide ( $\text{FeO}$ ) and 2.0 g of iron sulfide ( $\text{FeS}$ ), the molecule having more number of moles of metal atoms should be determined.

Concept Introduction:

Mole is SI unit which is used to measure the quantity of the substance. It is the quantity of a substance which contains same number of atoms as present in accurately 12.00 g of carbon-12 is known as mole

Number of moles is defined as the ratio of mass to the molar mass.

  $\text{Number of moles = }\frac{\text{Mass (g)}}{\text{Molar mass}}$

The ratio of mass of the given compound to the number of moles of compound is known as molar mass.

The one mole of any substance is equal to the Avogadro number i.e. $6.022\times {10}^{23}$ atoms.

Answer to Problem 5E

Number of moles of iron atom is more in 2.0 g of iron oxide in comparison to 2.0 g of iron sulfide.

Explanation of Solution

The given information is: 2.0 g of iron oxide ( $\text{FeO}$ ) and 2.0 g of iron sulfide ( $\text{FeS}$ )

First step is to calculate the molar mass of each molecule.

Molar mass of iron oxide = $1\times 55.845\text{ g/mole + 1}\times \text{16 g/mole}$

= $71.845\text{ g/mole}$

Molar mass of iron sulfide = $\text{1}\times \text{55}\text{.845 g/mole + 1}\times \text{32}\text{.065 g/mole}$

= $87.91\text{ g/mole}$

Now,

Number of moles of iron oxide is calculated as:

  $\text{Number of moles = }\frac{\text{Mass (g)}}{\text{Molar mass}}$

Put the values,

Number of moles of iron oxide = $\frac{\text{2}\text{.0 g}}{\text{71}\text{.845 g/mole}}$

Number of moles of iron oxide = $\text{0}\text{.028 mole}$

Number of moles of iron sulfide is calculated as:

  $\text{Number of moles = }\frac{\text{Mass (g)}}{\text{Molar mass}}$

Number of moles of iron sulfide = $\frac{\text{2}\text{.0 g}}{87.91\text{ g/mole}}$

Number of moles of iron sulfide = $\text{0}\text{.023 mole}$

The number of metal atoms, ${\text{Fe}}^{\text{2+}}$ in both the compounds is 1 as shown:

  $\text{FeO}\to {\text{Fe}}^{\text{2+}}{\text{ + O}}^{2-}$

  $\text{FeS}\to {\text{Fe}}^{\text{2+}}{\text{ + S}}^{2-}$

Hence, number of moles of iron atom is more in iron oxide in comparison to iron sulfide.